In general, methods of obtaining shale oil from oil shale include a direct heating method of bringing oil shale into direct contact with a heating medium and an indirect heating method of feeding oil shale into a reactor and heating the oil shale. Shale oil obtained by the heating process has properties similar to crude oil and thus has attracted attention as a next-generation oil resource.
Specifically, methods of recovering crude oil components from oil shale include a method of mining and retorting oil shale and a method of heating oil shale buried underground without mining. The retorting method includes a method of feeding oil shale into a reactor and heating the oil shale from the outside, a method of bringing oil shale into contact with combustion gas to be pyrolyzed, a method of brining a heated solid medium into contact with heated raw oil shale in a solid-solid phase, etc.
Unlike the above-described methods, the method of heating oil shale buried underground includes a method of recovering shale oil by electric heating or using heated combustion gas. According to this method, it is possible to obtain shale oil similar to that obtained by the existing retorting method or light oil of low boiling point.
Since both of these two methods heat nonconductive oil shale, a significant amount of kerogen components are converted into non-condensable gas, not shale oil, and thus, in most cases, the yield of crude oil components is very low, at less than 40%, on the basis of volatile matters contained in oil shale rocks.
Moreover, a significant amount of kerogen is decomposed when the oil shale is heated and remains in the form of carbon in the oil shale or in the form of high-boiling point components. As such, when the carbon components or high-boiling point components remaining in the oil shale are buried as they are, they cause soil or water pollution and thus are subjected to combustion.
At this time, the combustion energy generated by the combustion of waste oil shale is generally recovered and used as an energy source for pyrolysis of oil shale. During the combustion process, a large amount of carbon dioxide or carcinogens such as dioxin are emitted, which are the main cause of global warming and environmental pollution, and thus an alternative technique for emission suppression is required.
That is, the conventional processes of recovering crude oil components by directly or indirectly heating oil shale have a high cost of energy per unit price for crude oil production and cause environmental problems due to the emission of pollutants and carbon dioxide generated during the combustion of organic components in the residues, and thus the development of a crude oil recovery apparatus and method, which is environmentally friendly and can increase the crude oil production, has been required.